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The 2013 Detroit Tigers featured the most productive starting rotation since the 1997 Atlanta Braves, generating 25.5 Wins Above Replacement (Fangraphs fWAR). One reason is that the Tigers had five very talented pitchers. But another is that the Tigers enjoyed terrific health, and had only six pitchers start a game all year long. It’s much easier to be good when your best pitchers stay off the disabled list (DL) and keep showing up every fifth game.

Pitcher health is a topic that Jeff Zimmerman has been studying for years, and he’s done a fairly remarkable job of predicting which types of pitchers are most likely to make it through a season without a trip to the DL, and which are more likely to keep a team’s spot starter fully employed.

Obviously, pitching is incredibly stressful to the body, and all starters have some risk of going on the DL. However, certain factors tend to increase or reduce the chances of this happening. For example, pitchers who are older, heavier, and/or have recent trips to the DL are at greater risk of returning to the DL. To the contrary, pitchers who are younger, thinner, and pitched in college tend to have lower injury risks, at least at first. Regardless of their size pedigree, pitchers who throw a large number of breaking balls, or struggle to hit the strike zone, are also at increased risk of injury. Zimmerman tests his predictions after each season, and they hold up fairly well.

For 2014, Zimmerman has published his predictions for most of the likely rotation starters in baseball. The following charts represent my current predictions at the first-week rotations for the various NL Central teams, combined with Zimmerman’s injury predictions. For starters he did not specifically project, I’ve applied his disclosed risk factors to give my best estimate of how he would rank them.

Brewers Starter

In-Season DL Risk

Estrada

47%

Garza

51%

Gallardo

35%

Lohse

39%

Peralta

32%

Cardinals Starter

In-Season DL Risk

Wainwright

43%

Lynn

37%

Miller

30%

Wacha

30%

Kelly

34%

Cubs Starter

In-Season DL Risk

Samardzija

35%

Wood

31%

Jackson

33%

Rusin*

30%

Villanueva

43%

Pirates Starter

In-Season DL Risk

Liriano

45%

Locke

33%

Cole*

35%

Morton*

56%

Volquez

34%

Reds Starter

In-Season DL Risk

Latos

33%

Cueto*

52%

Bailey

36%

Leake

29%

Cingrani*

30%

The names of the players I had to estimate have asterisks next to them. Most of them were easy to predict because they were young pitchers with a fairly clean history. Johnny Cueto and Charlie Morton were more difficult because of their frequent trips to the DL, but I’m comfortable with the estimates.

If it looks like the Brewers’ rotation has a higher injury likelihood than the other NL Central rotations, you are correct. Both Matt Garza and Marco Estrada are high risks given their recent injury troubles. Kyle Lohse has a fairly decent injury history as of late, but is starting to get older. Yovani Gallardo and Wily Peralta have mostly avoided injury, but along with Estrada, they sometimes struggle to throw strikes, which is one of Zimmerman’s risk factors for future injury. By contrast, the Cardinals benefit from the relative youth of their rotation, and the Reds, despite Johnny Cueto, otherwise have a very durable staff.

If you compile the overall DL risk for each starting rotation, here is what you get:

NL Central Team

Median Starter DL Risk

Brewers

39%

Cardinals

34%

Cubs

33%

Pirates

35%

Reds

33%

Certainly, the Brewers are at higher risk (39%) than their NL Central competition for having a starter go on the DL this year. At the same time, even relatively healthy teams like the Cubs and Reds still have a one in three chance that a starter will miss significant time. So, when you hear people say that success in baseball has a lot to do with luck, that luck manifests itself over spreads like this. In 2011, the Brewers’ rotation, like the Tigers in 2013, needed only six starters, because the front five each pitched at least 158 innings. If this is the Brewers’ year for some injury luck, they are close enough to their competition to still come out of 2014 with the healthiest rotation of the lot. If those breaks don’t go their way, though, they will likely suffer more starter injuries than other NL Central teams, which will make their path to the postseason that much more challenging.

When at least one starter almost inevitably goes on the DL for each team, you’ll get their spot starter instead, perhaps for an extended period of time. Who will the spot starters be? Well, with the help of PECOTA from Baseball Prospectus, I suspect you’ll see these folks:

Team

Spot Starter

6th Starter Projected ERA (PECOTA)

Brewers

Tyler Thornburg

3.97

Cardinals

Jaime Garcia

3.62

Cubs

Carlos Villanueva

3.92

Pirates

Wandy Rodriguez

3.79

Reds

Jeff Francis

4.19

All five teams feature a spot starter who pretty much is not in the rotation for a reason. As usual, the Cardinals appear to have the best option. Notably, the Reds seem to have the least depth behind their rotation. This is a weakness worth watching. Although PECOTA thinks the Reds rotation is currently the class of the division, they don’t seem to have a backup plan if injuries strike.

The Brewers’ rotation has a higher likelihood of injury than their immediate competition. It remains to be seen whether that will interfere with what the Brewers hope will be a bounce-back season.

Follow Jonathan on Twitter @bachlaw.

fWAR statistics are from Fangraphs. PECOTA is published by Baseball Prospectus.

It does not, and Zimmerman now has Latos as a probable DL candidate to begin the year. But, I view that as part of how the regular season plays out, rather than the projection. So far, some bad luck for the Reds.

Looking at the 6tgh starters, it really seemsw that Central GMs are ready for “replacement rotation” issues. I cannot remember the last NL Central season that included viable 6th starters on each club.

So weight and not pitching in college have only a minor effect – it is really about youth and injury history. Otherwise, Peralta – the heaviest Brewer starter and a guy who didn’t pitch in college – would have a higher chance of going on the DL. Under the predictions above, he’s only 3% points away from the single lowest projection. Predicting injury based on youth and injury history is not particularly remarkable.